Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare idempotentHint=true and destructiveHint=false. The description adds valuable behavioral context beyond annotations: the paid nature ($0.05 per call), the HMAC-signed record mechanism, and the intended loop usage. These are informative and do not contradict annotations, though failure modes and rate limits are not disclosed.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is two sentences and front-loaded with the tool name and cost. Every sentence serves a purpose: the first defines the action and output, the second provides usage guidance and references verification. No wasted words, appropriately sized for the tool's complexity.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a complex tool with 14 parameters and nested objects, the description gives the essential context: core function, cost, usage pattern, and verification path. It does not mention required parameters (protocol, subject, intent) or the API key, but the schema covers these. Output schema exists, so return value details are unnecessary. The description is complete enough for initial tool selection.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema fully documents all 14 parameters. The description adds minimal parameter context, only hinting at 'optional settlement outcome' and mentioning 'binding hash, policy verdict, findings' which loosely map to the policy/outcome fields. This is sufficient but not enhanced beyond the baseline for complete schema coverage.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states a specific action: 'bind one x402 payment intent or MCP tool call to a canonical HMAC-signed record.' It identifies the resource (payment intent or tool call) and the result (signed record), and differentiates itself from sibling assurance_verify by referencing the 'free verify endpoint' for third-party checking.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explicitly instructs 'Loop it after every payment or tool call to build a tamper-evident audit trail,' giving clear when-to-use guidance. It also implies an alternative verification path via the 'free verify endpoint,' though it does not name the sibling tool assurance_verify directly or state explicit exclusion criteria.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.